荒漠草地植物稳定性氮同位素对水分变化的响应

Response of ^(15)N Isotope in Plant to Water Change in Desert Grassland

水分是影响荒漠地区植被分布的重要因素,近年来,我国西部地区的气候正向暖湿化发展,降水的变化势必会对植物N同位素的吸收、分配产生影响。利用15N标记法,通过不同的增水处理,研究古尔班通古特沙漠南缘标记样地和未标记样地植物N同位素吸收和分配对水分变化的响应,得出以下结论:①增水处理增加了对土壤水分的补给,显著提高了土壤水分含量;②未标记样地植物稳定性N同位素的Ndff值的变化范围为0.39～0.59,其最大值出现在30%增水处理,最小值出现在20%增水处理;③氮素标记后,样地植物稳定性N同位素Ndff值明显上升,其变化范围为15.27～31.24。从植物不同部位来看,植物吸收的氮素在植物茎中的分配比例最大,而在根中的分配比例最小。

Soil moisture content is an important factor for the distribution of desert vegetation.Climate warming-wetting trend is becoming more obvious in west China in recent years.The increase of precipitation will inevitably affect the N isotope absorption of plants.In this paper,the response of plant N isotope to soil moisture content change in the labeled and unlabeled sample plots in the southern marginal zone of the Gurbantunggut Desert were studied using the 15N labeling method.The results are as follows：（1） The water increase treatment increased significantly the soil moisture regime and soil moisture content;（2） Ndff in plants in the study area varied in a range from 0.39 to 0.59,its highest value occurred in a treatment case of soil moisture content increased by 30%,and the lowest one was found in a treatment case of soil moisture content increased by 20%;（3） The plant Ndff was increased significantly after applying nitrogenous fertilizer,and it varied in a range of 15.27-31.24.From the perspective of different parts of plant,the proportion of nitrogen absorbed by plant was the highest in stems,and it was the lowest in roots.